This invention relates to machines for producing movement between two paramagnetic members, one of which is an electromagnet. A specific machine of this type, referred to herein as applicant's earlier machine is disclosed in copending U.S. patent application Ser. No. 217,928 filed Dec. 18, 1980. The entire disclosure of this copending patent application is incorporated herein by reference.
An objective of this invention is to provide a highly efficient machine which is capable of operating at a high speed.
It has been found that the speed at which applicant's earlier machine operates cannot be increased without raising the voltage of the energizing power source. The operating speed has been found to be directly proportional to the voltage applied. When twelve volts were applied, the speed was one stroke per two seconds, and when twenty four volts were applied the speed was one stroke per second.
The behavior described in the preceding paragraph is attributable to the fact that the current flowing in the electromagnet windings did not immediately flow at the desired rate to produce an appropriate magnetomotive force. The current flow with respect to time followed an exponential curve wherein, when t.sub.max is the time required to reach the maximum current for the respective voltage and resistance, only 63.2% of the maximum current would flow at 0.25 of t.sub.max. When a potential of twelve volts was applied to a one ohm electromagnet coil, the current rose quickly to five or six amperes and then slowly rose to the maximum rate of twelve amperes. When twenty four volts were applied to the same coil, the current quickly rose to about twelve amperes and then slowly rose to twenty four amperes. When 120 volts are applied to a one ohm coil, twelve amperes will flow in only 0.079 second.
According to one aspect of the present invention, a machine is made to operate at a higher speed by shortening the time period required to establish the desired rate of current flow in an electromagnet. This is done by initially energizing the magnet with a higher voltage to achieve a rapid current increase, and then applying a lower voltage to maintain the current.
It has also been observed that when the windings of an electromagnet comprise two or more independently energizable coils, the time required to reach the maximum current flow in one coil, for a given voltage and coil resistance, can be shortened if the other coil already has current flowing therein.
Taking advantage of this principle, the invention also relates to a machine of the character described wherein the windings of an electromagnet include at least two coils. One coil is given a higher voltage at the commencement of the cycle to provide a rapid current rise, and another coil is given a lower voltage which quickly produces therein the maximum current for its respective resistance and voltage.